Right from the first track you are shot into one of the grunge era's greatest albums; heavy, melody, fierce and all together outstanding.
Soundgarden's superunknown i would argue is their greatest album, just because it seems like they've put so much effort into their sound and their songs, and the result is that you'll have hard rock songs like 'let me drown', 'my wave' and 'fresh tendrils' to name a few, then you are the given heavy, gritty, satisfying 'mailman' and '4th of july', not to mention the fantastic works of 'spoonman', 'she likes surprises' and of course 'black hole sun'.
But don't expect your head to be blown off all the way through however. Soundgarden tone things down with some tracks for a more, for want of a better word, relaxed feel with 'head down', 'half' and 'like suicide'. They know perfectly when to knock it back into gear however, and you won't be disappointed.
I've been listening to this album for years, and of course tastes vary from person to person, but if you are a rock fan, particularly a grunge fan, you need this album. Your collection just isn't complete without it.